The present invention relates to a method of manufacturing a semiconductor device of a multi-layer wire structure. More specifically, the present invention relates to a method of removing an undesired film formed between a metal wire in an upper-layered wiring structure and a metal wire in a lower-layered wiring structure at a bottom portion of a contact hole through which the metal wires of the upper-layered wiring and the lower-layered wiring are connected to each other.
In a method of manufacturing a semiconductor device of a multi-layer wire structure, a metal wire in an upper-layered wiring structure and a metal wire in a lower-layered wiring structure are connected to each other at a bottom portion of a contact hole. However, during the manufacturing process, an undesired film is formed between the metal wire in the upper-layered wiring structure and the metal wiring layer in the lower-layered wiring structure. Such an undesired film is, when the metal wires are made of copper, a copper diffusion preventing film for preventing copper atoms from being diffused from the copper wires into an insulation film formed adjacent to the copper wires, or when the metal wires are made of aluminium, a film for increasing reflow of aluminium or reliability of aluminium wire for long-term use.
Prior art will be explained in detail by using FIGS. 24 to 27 of the accompanying drawings, in a case where the metal wires are made of copper, and the undesired film is a copper diffusion preventing film for preventing copper atoms from being diffused from the copper wires.
FIG. 24 shows a semiconductor device of a multi-layer wire structure. FIG. 25 shows a cross-sectional view of the semiconductor device shown in FIG. 24. Copper diffusion preventing films 1211 and 1212 are formed around a metal wire 1201 formed in a lower-layered wiring structure 1291. The diffusion preventing films 1211 and 1212 are made of for example, silicon nitride and prevent copper atoms from diffusing into interlayered insulating films 1221 and 1292. Without the copper diffusion preventing films, the copper atoms will be flowed into the interlayered insulating films from being diffused from the copper wires, thereby a characteristic of a transistor is deteriorated. Accordingly, when the copper is used as a wire material, the copper diffusion preventing film is essential.
Next, as shown in FIG. 26, a copper diffusion preventing film 1213 made of silicon nitride is formed over the semiconductor structure shown in FIG. 25. Thereafter, the wire material whose main component is the copper is embedded in connecting holes 1205, 1206 formed in an interlayered insulating film 1292 and wire grooves 1294 formed in an upper-layered wiring structure 1293, thereby a semiconductor device having a multi-layer wire structure is manufactured.
Furthermore, FIG. 27 is an enlarged cross-sectional view showing a portion near the connecting hole 1205 of the semiconductor structure in which a wire material 1200 whose main component is the copper is embedded in the connecting holes and the wire groove of the semiconductor device shown in FIG. 26. As shown in FIG. 27, the copper diffusion preventing film exists at a bottom portion 1299 of the connecting hole 1205. A copper diffusion rate is extremely slow in the copper diffusion preventing film. Accordingly, when a current I1 is flowed through the wires 1200 and 1201 in the connecting hole 1205 as shown in FIG. 27, the copper diffusion preventing film portion prevents a movement of the copper atoms occurred due to the flow of the current, to cause a void (such a phenomenon that the wire material is moved in the wire, thereby a space is formed in the wire) and a hillock (such a phenomenon that the wire material is overflowed out the wire). Since the void and the hillock may often cause disconnection of the wires, a durable length of time of the wire is reduced. Furthermore, when a resistivity of the copper diffusion preventing film is more than that of the metal wires 1200 and 1201 whose main component is the copper, an equivalent resistance of the wires in the connecting hole 1205 is increased.
As described above, when the metal wire whose main component is the copper is used for the semiconductor device having the multi-layer wire structure, the copper diffusion preventing film for preventing the copper atom contained in the metal wire from diffusing therearound must be formed around the metal wire. However, in case of the wire structure as described above, the copper diffusion preventing film causes the disconnection of the wires due to an electromigration and a resistance increase of the wires at the connecting hole portion.